Conventionally, it has been known that an electrically conductive resin composite material wherein electrical conductivity is imparted can be obtained by incorporating an electrically conductive filler such as carbon black, carbon fiber and metal powder to a matrix resin such as thermosetting resin and thermoplastic resin.
However, it is necessary to add considerable amount of electrically conductive filler to impart high conductivity (preferably volume resistivity of 1×106 Ω·cm or less) to such kind of composite materials, which adversely affected physical properties of the matrix resin and resulted in a problem that the prepared composite material cannot exert the innate characteristics of the resin.
Therefore, a filler material has been demanded which enables to impart high conductivity even in small blending quantity.
As such an electrically conductive filler material, Japanese Laid-Open Patent Publication No. 2004-360099 discloses a fish-bone type carbonaceous microfiber body having excellent kneadability with resin and excellent electroconductivity.
The above-mentioned fish-bone type carbon fiber indicates the one having a structure in which a graphite network plane is inclined to the fiber axis. Other carbon fiber in which a graphite network plane is almost perpendicular to the fiber axis and carbon fiber which is not hollow are also known, and generally they are collectively referred to as carbon nanofiber.
On the other hand, carbon nanotubes having a structure in which a graphite network plane is approximately-parallel to the fiber axis have also been extensively studied.
As a method for producing such carbon nanotubes, a method by chemical vapor deposition (hereinafter referred to as “CVD method”) is known, including a method using catalyst metal supported on a support and a method using organic metal complex and the like as a catalyst without a support wherein catalyst metal is vapor-deposited in a reaction system.